For the engine case damage. EN may be able to help you (if you are not in a hurry). He has been pretty busy, but its about --20 Degree's so he will be indoors alot more.

Here is some aluminum welding repairs he did for someone.

Before:



After



Before:



After

Does anybody know what that black piece is for? Oil control maybe? Could it be left out?

That black metal piece is actually an oil "guide" of sorts......it gathers and directs the gear lube thrown behind the clutch basket back into the trans cavity It has a simple job, but it does need to be there.
Looks like with proper cleaning that could be welded ground flat and rethreaded.......the cases must be split anyways so it's not that big of a deal, I'd be more concerned with it happening again! lol.
Good luck,
--Ray

Sir,

Like everyone here has said, most RT-3 parts are available as NOS (new, old stock). Those that aren't are available in good, used condition on e-bay. I worked for San Diego Yamaha when the first RT-1s came out. In 1973, I raced one in Dist 36 and actually made Expert at a race at Cal Expo (got sent to Vietnam 7 days later...). Anyway, I kept a kick starter shaft that had SPUN nearly 270 degrees and NOT sheared in my toolbox to remind me of the need to keep it timed SPOT ON, and to USE THE DECOMPRESSION lever ALWAYS. With all that, just last Thursday, my daily rider (RT-3) kicked back and liked to have sent me over the bars! Timing, decomp, and kick it like you MEAN IT! Oh, and if the engine is warm, even a little, open the throttle about 1/2 way, decomp, and KICK like hell. Works every time.

Keep going! You will have a very enjoyable bike when you're done. Plus, every time you hit the streets, you can feel warm and fuzzy knowing that you are riding a street-legal air-cooled 2-stroke, and the EPA is just having a conniption fit over their not being anything they can do about it!

Mark Hamersly
2014 Dist 38 race number 169R

Thanks again to everyone. Hamersly that bike looks sweet! I definitely wasn't holding anything back when I kicked it to smithereens the other day, in fact I instantly regretting kicking it that damn hard when I felt things breaking as I went right through the kickback. But as you say, the timing is a critical factor and I hadn't adjusted it at that point. Also, I'm not entirely sure if the decompression unit is working or not, is there a simple way to check that?

Regarding the broken lip and screw holder in the case.... after a lot of looking around I seem to have located a right side crankcase (NOS I think, they are closed for the weekend so I need to call and get some more details). It's priced at 100 bucks so probably a better call than going through the extra time and expense of finding someone who can fix this current one by welding it.

I'm a bit curious though, if I go that route, are there any potential problems with pairing a new rightside crankcase to my existing old leftside crankcase?

Below is info on this topic from Gfrench, & DEET. Another owner of a 1973 RT3 (Larry Money is verifying if his is working)

1. The first thing to do is to make sure your cable is adjusted correctly. I usually hook mine up and adjust while it is out of the cylinder so I can see the movement and to make sure it has enough slack on the cable to allow the plunger to fully close. With all that said a good cleaning is a real good idea - That valve is real easy to take apart- Many times the carbon build up on the plunger part #1 will cause it to not close fully- The small o'ring part #2 if bad or missing will cause it to not seal once it is closed.




The Leak Down will expose "ANY" leak in the top end and the Main seals.
Piston needs to be at Bottom Dead Center (BDC).
In my opinion- The leak down is a MANDATORY step that everyone should do when it comes to these old bikes... cannot tell you how this simple test lead to all kinds of corrections I made on my Black Widow project that would still have me scratching my head to try to figure out. The other thing that should be automatic is take the extra time to replace the Old Main Crank Seals- Very easy to do and does not take long...The Black Widow today is one massive power house!!
An Airtight engine is the key to all Success!










2. No potential problems using a new right side case. Using Yama bond to seal the cases will do fine. Once everything is assembled, a leak test will show if you have a leak in between the cases.

Just thought I'd drop a little update on the mission... Thanks once again to everyone for the advice, and more (pntrbl).

So, since I'm new to this and didn't have a case splitter tool, I took the motor back down to my local Yamaha dealer who split it for me, and then I brought the pieces home to clean everything up while I wait for the parts to arrive. (As well as the broken parts, I also ordered a new oil seals kit, gasket kit, and carb kit) Figured that at least cleaning stuff should be within my mechanical limits. I guess it is, but wow, takes some time eh. Anyways, got the cases looking as good as I reckon I was going to get them. Figured that if everything goes well, I won't have to do this again for a long time (knock wood) so I might as well try and clean em up nice. Here's a couple of pics..







So yeah, glad that's out of the way, next up is the cylinder and head, any good tips on cleaning all those fins? I'm guessing the tip is "elbow grease and lots of patience" but who knows, maybe there's a timesaver or two out there?

You dont need any special tool to split a case (in my opinion)
You just need time, patience and carefulness.

Here is the redneck method:

Fisrt of all, you get every crankcase bolt out. You have to triple check yourself because you WILL forget some bolts.
Pretty much every time, engine crank cases have tome tabs that you can use to gentil split open the crankcase by tapping those tabs with a rubber hammer.
When you tap it several times gently, a split will appear between the crank cases.
You can then use a big flat screw driver and pry open the crank case gently to make sure you dont damage the soft aluminum casing. Prying each corner gently until it pops off. (you use parts of the crankcase where you dont need a perfect seal in case you damage anything, like where the mountings are, where there is no oil.)
The crankshaft will stay in one or the other crank case.
You can then use any method you like to remove the crankshaft from the remaining bearing. (easy) (no fancy tools required either)

For the fins, i use time, patience and carefulness again.
With a small flat screw driver you can remove all the dirt and gunk and with brake cleaner you can clean it very good. You can use the flat screw driver to push a rag in the hard spots to clean it perfectly.
You can then paint it if you want.
OR you can simply bring it to a machine shop and they will put it in their part cleaner machine and it will take 5 minutes and it will look new again.

While you are in your crank case, take the time to replace every transmission bearing. There are not expensive and it is worth it.
Obviously you need to replace the crankshaft bearings as well.
I would recommend if it is not already planned that you replace every seal along with every gasket to make sure there is no leaks.

---Ben

All you need to split the cases without risking "pry damage" is a simple two-bolt puller (a steering wheel puller will often work) that can usually be rented free at an auto parts store or purchased very inexpensively... You can even make a puller that will work out of some all-thread, a couple of bolts and nuts and some scrap angle iron or channel.

Ive never used a puller of any sort to split the crank case on motorcycle engines and ive rebuilt dozens of engines and they never had any problems. You just have to be carefull. It takes me more time to set up the puller than to do it my old redneck way